This invention relates to reinforced fabric constructions and more particularly to antistatic reinforced fabric constructions.
Resistance to the buildup of static electricity is required in addition to physical properties such as adequate tear strength for fabrics in numerous applications, such as in the mining and tunneling industries, the aerospace and electronics industries, and the medical field, among others. Laminated fabrics, i.e., fabric-reinforced sheets of vinyl or the like, are known to provide superior physical properties, and are also commercially available with varying levels of antistatic properties. One such product is a 3-ply laminate consisting of a substrate of synthetic scrim between two layers of vinyl film one or both of which contain carbon. A 4-ply laminate is also available in which a layer of carbon is buried alongside the scrim between two outer layers of PVC film. Such a construction makes it possible to choose a color other than carbon black for a laminated fabric with antistatic properties, and therefore has some advantage over simpler constructions from a general aesthetic standpoint, and also from a safety standpoint in applications where color is important. For example, white or yellow fabric is preferred in the mining industry for increased visibility underground. However, a 4-ply laminate generally requires additional material and is more complex to manufacture than a 3-ply laminate.
Another known method of imparting antistatic properties involves plastisol coating a scrim with a film containing an antistatic ingredient. However, such coated fabrics have been found to have unstable electrical properties. This is believed to be due to the temperature conditions encountered during the plastisol coating process, as a result of which the antistatic ingredient "blooms" to the surface and then dissipates over time. Plastisol coating is also time-consuming, which results in relatively high production costs and relatively low production rates, two disadvantages which have not heretofore been outweighed by the quality of the resulting antistatic product.
All of the known antistatic fabric constructions suffer from certain shortcomings, either in their electrical properties, availability of colors, fabric strength, other physical properties, or cost.